Eastwood Pottery Posted September 6, 2018 Report Share Posted September 6, 2018 I am new to the community. My website is Eastwood Pottery I have a question regarding Hannah's Fake Blue Ash glaze. My glaze always comes out brown. I left out the RIO and just used the Cobalt Oxide but I still for the life of me cannot get blue. Does anyone out there have success using the blue ash glaze and do you use cobalt oxide as in the recipe? Link to comment Share on other sites More sharing options...
neilestrick Posted September 6, 2018 Report Share Posted September 6, 2018 @Eastwood Pottery Can you post the recipe you're using, as well as a picture of your results? Link to comment Share on other sites More sharing options...
Eastwood Pottery Posted September 6, 2018 Author Report Share Posted September 6, 2018 redart 56 whiting 29 strontium carb 10 frit 3195 5 cobalt oxide 1.3 Link to comment Share on other sites More sharing options...
Benzine Posted September 6, 2018 Report Share Posted September 6, 2018 That looks underfired compared to the examples I've seen. Link to comment Share on other sites More sharing options...
neilestrick Posted September 6, 2018 Report Share Posted September 6, 2018 @Eastwood Pottery Are you sure your cobalt is cobalt? At 1.3% you should be getting a blue background for sure. Have you used the same cobalt in other glazes? It doesn't look underfired to me. Plenty runny. Link to comment Share on other sites More sharing options...
Eastwood Pottery Posted September 6, 2018 Author Report Share Posted September 6, 2018 I am sure it was1.3. Tested twice. Link to comment Share on other sites More sharing options...
neilestrick Posted September 6, 2018 Report Share Posted September 6, 2018 2 minutes ago, Eastwood Pottery said: I am sure it was1.3. Tested twice. But are your sure that your cobalt is actually cobalt, and not some other material of similar raw color like manganese or a black stain? Have you used that cobalt to make blue in other glaze batches? Link to comment Share on other sites More sharing options...
Eastwood Pottery Posted September 6, 2018 Author Report Share Posted September 6, 2018 I have not used it in anything else. It is labeled cobalt oxide. One I worry the supplier messed up, and it wasn’t cheap. Link to comment Share on other sites More sharing options...
neilestrick Posted September 6, 2018 Report Share Posted September 6, 2018 11 minutes ago, Eastwood Pottery said: I have not used it in anything else. It is labeled cobalt oxide. One I worry the supplier messed up, and it wasn’t cheap. I would test it in a basic clear glaze and see what color you get. At 1.3% it should be blue. Link to comment Share on other sites More sharing options...
Eastwood Pottery Posted September 6, 2018 Author Report Share Posted September 6, 2018 I am gonna try that it does look similiar to black iron oxide that I have. Link to comment Share on other sites More sharing options...
Benzine Posted September 6, 2018 Report Share Posted September 6, 2018 31 minutes ago, neilestrick said: @Eastwood Pottery Are you sure your cobalt is cobalt? At 1.3% you should be getting a blue background for sure. Have you used the same cobalt in other glazes? It doesn't look underfired to me. Plenty runny. I'm no expert, and I would agree that it looks plenty runny, but some of the runny bits look "puffy" and more matte, like an underfired glaze. I have zero experience with this glaze, just something that I noticed. Link to comment Share on other sites More sharing options...
Min Posted September 6, 2018 Report Share Posted September 6, 2018 @Eastwood Pottery, hold a magnet up to what you bought as cobalt, it won't attract if it is cobalt but if it's synthetic black iron oxide it will. Link to comment Share on other sites More sharing options...
Eastwood Pottery Posted September 7, 2018 Author Report Share Posted September 7, 2018 Thanks min what a wonderful suggestion. Link to comment Share on other sites More sharing options...
curt Posted September 7, 2018 Report Share Posted September 7, 2018 Brown is almost always caused by iron in my experience. Redart has a massive amount of iron in it. This is probably completely overwhelming the much smaller amount of cobalt in the recipe. Try substituting some other kaolin/clay for, say, half of the red art. Link to comment Share on other sites More sharing options...
GEP Posted September 7, 2018 Report Share Posted September 7, 2018 I agree with curt. That much redart will make any glaze brown. Link to comment Share on other sites More sharing options...
neilestrick Posted September 7, 2018 Report Share Posted September 7, 2018 18 minutes ago, curt said: Brown is almost always caused by iron in my experience. Redart has a massive amount of iron in it. This is probably completely overwhelming the much smaller amount of cobalt in the recipe. Try substituting some other kaolin/clay for, say, half of the red art. Redart has about 7% iron, and by the time it's diluted with everything else in the recipe it's about 4.1%, which is not all that much. You can see a tile of that recipe HERE. Link to comment Share on other sites More sharing options...
liambesaw Posted September 7, 2018 Report Share Posted September 7, 2018 4 minutes ago, neilestrick said: Redart has about 7% iron, and by the time it's diluted with everything else in the recipe it's about 4.1%, which is not all that much. You can see a tile of that recipe HERE. That's even on a red body Link to comment Share on other sites More sharing options...
GEP Posted September 7, 2018 Report Share Posted September 7, 2018 The recipe in Neil’s link notes that they used a local red clay instead of redart. I would still recommend to OP to replace the redart with something lighter. Link to comment Share on other sites More sharing options...
neilestrick Posted September 7, 2018 Report Share Posted September 7, 2018 1 minute ago, liambesaw said: That's even on a red body Yep. I've got a blue fake ash in my studio that's got 3% iron and 1% cobalt carb, and it's plenty blue. Link to comment Share on other sites More sharing options...
neilestrick Posted September 7, 2018 Report Share Posted September 7, 2018 2 minutes ago, GEP said: The recipe in Neil’s link notes that they used a local red clay instead of redart. I would still recommend to OP to replace the redart with something lighter. Even so, 4% iron isn't enough to wipe out 1.3% cobalt and turn it black with no hint of blue whatsoever. Link to comment Share on other sites More sharing options...
GEP Posted September 7, 2018 Report Share Posted September 7, 2018 20 minutes ago, neilestrick said: Even so, 4% iron isn't enough to wipe out 1.3% cobalt and turn it black with no hint of blue whatsoever. I’ll take your word for it. I admittedly do not have much experience with blue glazes. @Eastwood Pottery could you possibly have mis-measured the cobalt oxide? Oxide is super-concentrated, far more than cobalt carb. The oxide is often a component in black stains. A small measuring mistake can make a big difference. Link to comment Share on other sites More sharing options...
Chilly Posted September 7, 2018 Report Share Posted September 7, 2018 Could an admin please correct the typo in the title of this thread, otherwise it won't be found in future searches for "blue". Many thanks. Link to comment Share on other sites More sharing options...
Magnolia Mud Research Posted September 7, 2018 Report Share Posted September 7, 2018 My guess is that you are not using cobalt oxide; probably manganese oxide; both materials are black powders. Try this: take a small white porcelain test tile, and mix a little bit of your "cobalt oxide" a little bit of baking soda in water and make marks on the test tile. Then fire normally. If the marks are not a strong blue, your material is not cobalt oxide!. As a footnote, I always use cobalt carbonate rather than cobalt oxide because the carbonate form is cheaper per atom of cobalt AND cobalt carbonate is NOT black. LT Link to comment Share on other sites More sharing options...
dhPotter Posted September 7, 2018 Report Share Posted September 7, 2018 This glaze is going to be a dark blue. I use 2% cobalt carbonate. Link to comment Share on other sites More sharing options...
neilestrick Posted September 7, 2018 Report Share Posted September 7, 2018 Here are a few other examples of how it should look: http://paulahendersonpots.blogspot.com/2011/03/potting-again.html https://i.pinimg.com/originals/cf/de/90/cfde90796b4eb73830cd9e97f70e8fc1.jpg http://cone6pots.ning.com/photo/oct2011-023-roundedbowl-hfablue-above-vsbovernutmeg Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.